The present invention relates generally to precision welding. More particularly the invention relates to a welding device according to the preamble of claim 1.
Technical solutions for automatic welding have been known for decades. Below follows some examples of how a welding device can be controlled to apply welding material between two work pieces so as to connect these mechanically with one another.
EP 423 088 discloses a method for automatic multi-run welding of butt joints. Here, a sensor having a feeler rod with a ball-shaped tip oscillates transverse to the weld joint to scan the joint at several portions. Thus, the sensor determines a contour of the joint, and the welding can be adapted accordingly as the welding device progresses through the joint.
JP 59209483 describes a solution for detecting a groove width and in response thereto controlling a welding process. A pair of stylus sensors slides orthogonally across the groove, and a displacement meter determines the width of the groove based on contacts between the sensor and the groove at various points.
U.S. Pat. No. 3,612,818 reveals an arrangement for controlling the application of weld metal in electric welding. According to one described alternative the geometric properties of a V-joint is detected via a pair of scanning rolls, which are pressed against the edges of the joint. The rolls are mounted on a carriage where they are hinged on a common point of rotation.
This design is advantageous compared to the former because it allows a continuous measurement of the joint properties. Thus, a relatively high accuracy can be attained. However, due to the design, the arrangement is limited to be applied in joint profiles where the joint edges deviate considerably from being fully vertical surfaces. For example, the arrangement cannot be used in joints where the edges constitute essentially parallel surfaces. Particularly, it is impossible to use the arrangement for welding comparatively thick work pieces with narrow joints having steep edges.